feat(journal): pin the report-tone contract — a narrative engineering report, not a diary (#2711)

[rysweet]

Closes #2711.

What

Simard's daily journal must read as a professional NARRATIVE ENGINEERING & RESEARCH REPORT — third-person, factual, reflective prose — and never as a personal diary ("Dear diary", confessional "I, Simard", cutesy sign-offs).

That voice is already enforced in three places on main:

• the two journal recipe prompts (journal-narrative.yaml, journal-plain-language.yaml) mandate the report voice and forbid the diary voice;
• the deterministic offline pipeline scrubs diary phrasing via the "dear diary" -> "" glossary;
• lib tests assert its absence in generated output.

The one untested surface was the prompt assets themselves plus the end-to-end anti-diary guarantee. This PR pins that contract and closes the gap.

Changes (additive, back-compatible)

• tests/journal_report_tone_contract.rs — hermetic, offline test:
  • Part A: both journal recipe YAMLs MANDATE the report voice and FORBID the diary voice. Asserts the prohibition instruction is present (not the mere absence of "Dear diary", which legitimately appears inside the negative instruction and the glossary).
  • Part B: injected diary phrasing is scrubbed from the generated narrative; both active-day and quiet-day pipelines stay report-framed (## Overview, no I, Simard); glossary backstop retained.
• src/journal/types.rs — fix a stale "diary-like narrative" module doc comment to match the enforced third-person report voice.
• Docs — docs/concepts/journal-report-tone-contract.md (the tone contract), linked from docs/index.md and the mkdocs Concepts nav.

Verification

• cargo build ✅
• cargo test --test journal_report_tone_contract — 6/6 pass ✅
• cargo test --lib journal:: — 60/60 pass ✅
• pre-commit (fmt, clippy) and pre-push (release lib tests, all-targets clippy) hooks pass — committed/pushed without --no-verify ✅

No production behavior change, no new identifiers, no stray println!/eprintln!.

Co-authored-by: Copilot 223556219+Copilot@users.noreply.github.com

[github-actions]

📊 Coverage Summary

Generated by cargo llvm-cov --workspace --summary-only (nightly, excluding test files)

Module	Lines	Covered	Coverage
Total	146828	122478	83.4%

_{Coverage data from CI run. Test files matching tests?/ are excluded from line counts.}